Transmission Characters Analysis Of Gearbox System With Consideration Of Thermal Deformation And Friction

During the gear transmission process, gear system shows complex dynamic response characteristics under the influence of some nonlinear factors such as friction, backlash, and time-varying mesh stiffness, thereby having a great influence on transmission performance. Meanwhile, under the high speed and high load transmission working condition, the heat can not be ignored, and the gear dynamic characteristics can also be changed due to thermal deformation. Based on the basic theory of gear nonlinear dynamics, the spur gear dynamics model considering friction and temperature is built and studied.Based on the analysis of gear meshing process, the mechanism of tooth surface friction is studied, and the expression of friction is obtained. Dynamic model of spur gear transmission systems is built by using centralized mass method which take friction, backlash, time-varying meshing stiffness and contact ratio into account. Based on the theory of mechanical thermal deformation, the influence of temperature on the gear dynamic response is considered, and the dynamic model with temperature effect is established. The numerical solution is carried out by employing4-5order Runge-Kutta method, time history diagram, spectrogram, phase diagram and poincare section are used to analyze the system motion characteristics. The results show that the torque fluctuation frequency and backlash have obvious impacts on the responses of gear system, friction coefficient and temperature only have obvious influence when torque fluctuation is high enough.To combine gear dynamic response with gear rattle and transmission efficiency, a rattle index and friction power loss are proposed and the change rules of transmission characteristics with different parameters are analyzed. Meanwhile the coupling relation between each parameter is studied. The results shows that friction coefficient and torque fluctuation frequency have obvious impacts on both rattle phenomenon and friction power loss, the influence of backlash on these two indexes appears differently depended on friction coefficient, and the temperature only have influence on rattle phenomenon. To improve the rattle phenomenon and reduce friction power loss, it is advised to select small friction coefficient, low torque fluctuation frequency, appropriate backlash, but working environment temperature control is not the key point.